The present invention relates to a method for manufacturing capacitor of a semiconductor device, and more particularly to a capacitor having a tapered cylindrical storage node to prevent leaning of the cylindrical storage node and a method for manufacturing the same.
As the semiconductor memory devices such as DRAMs are highly integrated, the width of a capacitor, which serves as a storage for storing data in the memory device, is narrower. The capacitor is made of a dielectric layer interposed between a storage node and a plate node, and the capacitance is proportional to the surface area of the node and a dielectric constant of the dielectric layer and inversely proportional to a distance between the nodes, i.e. a thickness of the dielectric layer.
Accordingly, in order to obtain a capacitor of high capacity, it is required to use a dielectric layer having a large dielectric constant, and/or to enlarge the surface area of the node, and/or to reduce a distant between the nodes. However, limitations exist as to the extent the distant between the nodes, i.e. a thickness of the dielectric layer, can be reduced, and as such the studies were focused on finding ways of using a dielectric layer having a large dielectric constant or enlarging the surface area of the node to form a high capacity capacitor.
A typical method for enlarging the surface area of the node includes a method of forming a three dimensional storage node having a concave or cylindrical shape. The cylindrical shape storage node is considered more advantageous to realize a capacitor of high capacity than a concave type storage node, because it has larger node area.
However, although not shown and described in detail, a dip-out process for removing a mold insulation layer is carried out in order to form the cylindrical storage node and, during a drying procedure in the dip-out process, a storage node could lean to cause bridging of two adjacent storage nodes due to the surface tension of deionized water (DIW) and the increased height of the storage node.
Accordingly, as a way to ensure and prevent the leaning of the storage node and the bridging between the adjacent storage nodes, it was required to secure the cell-to-cell spacing of more than the desired distance and to reduce the height of the storage nodes.
However, since the spacing between cells is already narrow from the mask state due to the reduction of design rule to achieve high integration of semiconductor devices, it is difficult to ensure the adequate cell-to-cell spacing using a conventional etching process and a cylindrical storage node forming process, and thus it is impossible to prevent the leaning of the cylindrical storage node. Consequently, it is impossible to form stably a cylindrical capacitor when it is made in a conventional way as described above.